1. Field of the Invention
The present invention relates to a filter attachment machine for a filter cigarette manufacturing system, and more particularly, to a paste transfer apparatus incorporated in the filter attachment machine for applying paste to tip paper.
2. Description of the Related Art
In recent years tobacco with mild taste has been in demand. To meet the demand, filter cigarettes each having a filter at one end of a cigarette are on the market. Filters are attached to respective cigarettes in a filter attachment machine of a cigarette manufacturing system, by wrapping a piece of tip paper around a cigarette and a filter. To this end, typically a wrapping section provided in the filter attachment machine is supplied with filter plugs each interposed between two cigarettes, as well as pieces of tip paper applied with paste.
In connection with the supply of pieces of tip paper applied with paste, the filter attachment machine has a transport path for guiding the tip paper unrolled from a paper roll to the wrapping section, and a paste applicator is arranged so as to face the transport path for applying paste to one side of the tip paper. On the downstream side of the paste applicator, a cutter is arranged for cutting the tip paper, which has been applied with paste, into pieces with a predetermined length. The pieces of tip paper thus cut by the cutter are supplied to the wrapping section, where each piece of tip paper is wrapped around two cigarettes with a filter plug therebetween. Double-length filter cigarettes obtained in this manner, each connected by a piece of tip paper, are cut in the center of the filter plug, thereby obtaining individual filter cigarettes.
A paste transfer apparatus known in the art as the aforementioned paste applicator comprises a paste supply roller which rotates while being supplied with paste, and a paste transfer roller disposed in rolling contact with both the paste supply roller and the surface of tip paper to be applied with paste. Paste adhering to the paste supply roller is transferred via the paste transfer roller to the tip paper in the form of a layer. In order for the tip paper to be properly wound around cigarettes and filter plugs in the wrapping section of the filter attachment machine, the thickness of the paste layer transferred to the tip paper must be within a suitable range.
Conventionally, therefore, the contact angle over which the tip paper is brought into contact with the paste transfer roller is fixed so that the paste layer may have a suitable thickness when the tip paper is traveling at a set speed. Thus, while the operating conditions of the cigarette manufacturing system including the tip paper traveling speed remain the same, the paste layer formed on the tip paper by transferring paste adhering to the paste supply roller to the tip paper via the paste transfer roller has a constant thickness.
However, the operating conditions of the cigarette manufacturing system are not always the same; for example, the traveling speed of the tip paper can change. In such cases, in the conventional paste transfer apparatus in which the paste transfer roller and the tip paper are always in rolling contact at a fixed contact angle, the amount of paste transferred to the tip paper from the paste transfer roller varies. Specifically, when the tip paper traveling speed decreases below the set speed, excessive paste is transferred to the tip paper. In this case, if the paste used has high adhesive strength, the tip paper may possibly be entwined round the paste transfer roller. Conversely, when the tip paper traveling speed increases above the set speed, the paste is insufficiently transferred, possibly causing defective wrapping of the tip paper around cigarettes and filter plugs.